Hi, everybody.大家好！I&#39m here at Children&#39s National Medical Center in Washington, D.C., visiting with some kids being treated here all the time for asthma and other breathing problems.此刻，我在华盛顿特区的国家儿童医疗中心，看望在这里接受治疗的哮喘和其它呼吸系统疾病的患儿。Often, these illnesses are aggravated by air pollution-pollution fr

Hi, everybody.大家好！I&#39m here at Children&#39s National Medical Center in Washington, D.C., visiting with some kids being treated here all the time for asthma and other breathing problems.此刻，我在华盛顿特区的国家儿童医疗中心，看望在这里接受治疗的哮喘和其它呼吸系统疾病的患儿。Often, these illnesses are aggravated by air pollution-pollution fr